The present invention relates to explosives for priming explosive devices, for example ammunition cartridges and detonators.
Conventional priming composition for small arms cartridges comprises lead styphnate, and for detonators comprises lead azide or a mixture of lead azide and lead styphnate, as the primary explosive. German Patent Specification 289016 suggests the double salt lead nitrato-hypophosphite as a primary explosive. That patent issued in 1922, but there does not appear to have been any practical use of the double salt until Brun and Burns suggested its use as a relatively minor ingredient in a priming composition described in U.S. Pat. No. 2,116,878. The double salt was to be produced by a technique as described in U.S. Pat. No. 2,160,469. However, that specification indicates that lead nitrato-hypophosphite is not a satisfactory substitute for azide or styphnate because of its inability to ignite secondary explosives.
The present inventors have found that double salts of hypophosphites can be substituted for azides and styphnates as primary explosives. The present invention therefore provides a priming (or initiating) composition whereof the primary explosive is wholly or mostly constituted by a "multiple" salt of a hypophosphite. In the present specification the term "multiple" salt is used to indicate a salt produced by co-crystallisation of two or more component salts. The invention also provides a method of initiating a secondary explosive comprising the step of exploding such a priming composition.
The composition may include other, preferably non-explosive, ingredients, for example a frictionator and/or a fuel. The multiple salt preferably comprises a nitrate component and a hypophosphite component. Preferably both components are lead salts.